1. Field of the Invention
The present invention relates to a photosensitive planographic printing plate precursor that can be loaded immediately after exposure into a printing machine so that printing is started without any special processing such as development.
2. Description of the Related Art
According to prior art, in order to obtain prints by using a photosensitive planographic printing plate precursor (hereinafter referred to as a printing plate precursor on occasion), it is necessary to carry out a procedure that comprises exposing the printing plate precursor image-wise and developing the exposed plate with an appropriate developer so that a planographic printing plate precursor having a lipophilic image portion and a hydrophilic non-image portion is produced. After that, agum coating is applied in order to protect the planographic printing plate precursor. Following such wet processing, the planographic printing plate precursor is loaded into a printing machine and printing is started.
For developing processing as a processing step after exposure, a developer, which is an alkaline liquid or an alkaline liquid containing an organic solvent, is generally used. In this regard, because of environmental problems due to waste liquids of the developer or maintenance problems of automated developing machines, there is a demand for a system that requires no developing step.
In order to solve these problems, Japanese Patent Application National Publication (Laid-Open) No. 6-502,931 proposes a photosensitive planographic printing plate precursor having a double-layered photosensitive layer comprising a photosensitive hydrophilic layer and a photosensitive hydrophobic layer provided thereon. This photosensitive planographic printing plate precursor can be loaded immediately after exposure into a printing machine so that printing is started without any processing after exposure. This photosensitive planographic printing plate precursor, however, has a durability problem in printing because the adhesion between the upper layer and the lower layer is insufficient.
WO 96/34316 discloses a photosensitive planographic printing plate precursor having a single-layered photosensitive layer composed of a polymer comprising a photo-hardenable group and an acid group or an acid salt group and a photopolymerization initiator. This photosensitive planographic printing plate precursor can also be loaded immediately after exposure into a printing machine so that printing is started without any processing after exposure. This photosensitive planographic printing plate precursor, however, has insufficient durability in printing. Therefore, the durability in printing becomes very poor if the pH value of dampening water in printing is shifted so as to become alkaline.
Further, Japanese Patent Application Laid-Open (JP-A) No. 47-8,657 discloses that a photosensitive planographic printing plate precursor that can be loaded immediately after exposure into a printing machine so that printing is started without any processing after exposure can be obtained by a photosensitive composition comprising polyvinylpyrrolidone, a polymeric polycarboxylic acid, an olefinically unsaturated monomer, a photopolymerization initiator, and the like. However, the use of the photopolymerization initiator disclosed therein presented problems in terms of sensitivity and fogging after exposure.